Here it is what I've read for Blender.

Not much code had to be changed to integrate SSS into the render pipeline.

- For each material with SSS, a preprocessing pass is done similar to
environment mapping.
- This pass is fully threaded, and works similar to rendering a regular
layer.
- For each tile, two zbuffers are created, one with the frontmost faces and
one with the backmost faces.
- The points on these faces are then shaded, but with only diffuse shading,
including AO and radiosity.
- These points are all collected into a list, with their color, 3d
coordinate and area.
- Using the list of points, an octree is built for quick lookup during
rendering.
- When doing regular rendering, instead of using the diffuse shading, a
color computed by taking a weighted average of points in the octree is
used.

And for Povray are these steps easy to implement or not?

Post a reply to this message

Antonio Ferrari wrote:
> - For each tile, two zbuffers are created, one with the frontmost faces and
> one with the backmost faces.
<snip>
> And for Povray are these steps easy to implement or not?

POV-Ray is a ray-tracer, not a scanline renderer. The algorithms for POV-Ray
would be different (and simpler).

	Thorsten

Post a reply to this message

Thorsten Froehlich <tho### [at] trfde> wrote:
> Antonio Ferrari wrote:
> > - For each tile, two zbuffers are created, one with the frontmost faces and
> > one with the backmost faces.
> <snip>
> > And for Povray are these steps easy to implement or not?
>
> POV-Ray is a ray-tracer, not a scanline renderer. The algorithms for POV-Ray
> would be different (and simpler).
>
>  Thorsten

Ok... I was simply wondering if many features that some applications nowdays
have will be added also to Povray. SSS is only one of them. I'de like to see
Povray growing up more rapidly and overclass many other programs (yafray,
etc.). I love Povray but it seems it's loosing many opportunities. It's
only my opinion :-)

Post a reply to this message

Antonio Ferrari wrote:
<remove>
> And for Povray are these steps easy to implement or not?

You can do something similar with MegaPOV. Using the projection pattern 
you can convert the 'light map' into a pigment and blur it using the 
average pigment. I made some posts a long time ago about this very same 
thing to p.b.images. The method can render very slowly, though.

Funny you should mention Blender, btw. That post in p.o-t led me to 
Blender's website, and it looks like the newer version has a bunch of 
new features that weren't present in the version I already had. I'm 
blown away by how fast you can render hair, SSS, focal blur.... I've got 
me a new toy :) :)


Sam

Post a reply to this message

"Antonio Ferrari" <nomail@nomail> wrote:

> Ok... I was simply wondering if many features that some applications nowdays
> have will be added also to Povray. SSS is only one of them. I'de like to see
> Povray growing up more rapidly and overclass many other programs (yafray,
> etc.). I love Povray but it seems it's loosing many opportunities. It's
> only my opinion :-)

I confess that I agree, but now is probably a good time to thank everyone
who has developed POV-Ray for their effort.  Assuming most of the
developers have a life outside of this, it's all the more impressive.  That
said, subsurface scattering sure would be a great addition.  I know media is
more robust, but I can never get that to work right.  Oh, and someone has
already implemented this in POV-Ray, but it's probably not for sharing
(look at the last line):

http://www-static.cc.gatech.edu/grads/t/Sarah.Tariq/a_practical_model_for_subsurface.html

 - Ricky

Post a reply to this message

"Samuel Benge" <stb### [at] THIShotmailcom> schreef in bericht 
news:471e6964@news.povray.org...
> Antonio Ferrari wrote:
> <remove>
>> And for Povray are these steps easy to implement or not?
>
> You can do something similar with MegaPOV. Using the projection pattern 
> you can convert the 'light map' into a pigment and blur it using the 
> average pigment. I made some posts a long time ago about this very same 
> thing to p.b.images. The method can render very slowly, though.
>
> Funny you should mention Blender, btw. That post in p.o-t led me to 
> Blender's website, and it looks like the newer version has a bunch of new 
> features that weren't present in the version I already had. I'm blown away 
> by how fast you can render hair, SSS, focal blur.... I've got me a new toy 
> :) :)
>
>

Hmmm... time to go back to Blender, I guess. I shall have a look too.
Wish I had some time to really learn Blender, but as I can set my own 
priorities I am the only one to blame :-)

Thomas

Post a reply to this message

> I confess that I agree, but now is probably a good time to thank everyone
> who has developed POV-Ray for their effort.  Assuming most of the
> developers have a life outside of this, it's all the more impressive.  That
> said, subsurface scattering sure would be a great addition.  I know media is
> more robust, but I can never get that to work right.  Oh, and someone has
> already implemented this in POV-Ray, but it's probably not for sharing
> (look at the last line):
>
>
http://www-static.cc.gatech.edu/grads/t/Sarah.Tariq/a_practical_model_for_subsurface.html


Yes. I also have a work and I'm out of my house from 7am to 20pm. I have
also a little child of one year old. But in spite of this I'm trying to
develop a patch that allows to use media ii such a way that can model sss.
I'm trying to do this adding a new pattern that can be used in density
contest. DF3 files could be used, but they need a double pass to render and
an external program. If my idea will be OK, I hove to model a density
pattern that grows exponentially with the (minimal) distance from a generic
surface. It's just an aid to avoid df3 alternative. I've already talked of
these topics in other posts. Obviously rendering time grows up a lot.

I'm already at a good point of developement and I've already obtained good
results. Unfortunately not always I've found a sufficient support in this
forum. So I had to study and debug by my own. Anyway thanks to everyone
that have helped me.

Antonio

P.S. The source code of Sarah Tariq is not available. Can anyone try to
contact her?

Post a reply to this message

Antonio Ferrari napsal(a):
> 
>> I confess that I agree, but now is probably a good time to thank everyone
>> who has developed POV-Ray for their effort.  Assuming most of the
>> developers have a life outside of this, it's all the more impressive.  That
>> said, subsurface scattering sure would be a great addition.  I know media is
>> more robust, but I can never get that to work right.  Oh, and someone has
>> already implemented this in POV-Ray, but it's probably not for sharing
>> (look at the last line):
>>
>>
http://www-static.cc.gatech.edu/grads/t/Sarah.Tariq/a_practical_model_for_subsurface.html
> 
> 
> Yes. I also have a work and I'm out of my house from 7am to 20pm. I have
> also a little child of one year old. But in spite of this I'm trying to
> develop a patch that allows to use media ii such a way that can model sss.
> I'm trying to do this adding a new pattern that can be used in density
> contest. DF3 files could be used, but they need a double pass to render and
> an external program. If my idea will be OK, I hove to model a density
> pattern that grows exponentially with the (minimal) distance from a generic
> surface. It's just an aid to avoid df3 alternative. I've already talked of
> these topics in other posts. Obviously rendering time grows up a lot.
> 
> I'm already at a good point of developement and I've already obtained good
> results. Unfortunately not always I've found a sufficient support in this
> forum. So I had to study and debug by my own. Anyway thanks to everyone
> that have helped me.
> 
> Antonio
> 
> P.S. The source code of Sarah Tariq is not available. Can anyone try to
> contact her?
> 
> 
> 
I thought that the skin has a constant density that is quite high plus 
probably some rough surface (epidermis) over it and even inserting some 
bones.
You can use any function or pattern as the media density; working out 
the function itself is probably impossible if you are using meshes.

Post a reply to this message

Jan Dvorak <jan### [at] centrumcz> wrote:
> I thought that the skin has a constant density that is quite high plus
> probably some rough surface (epidermis) over it and even inserting some
> bones.

Yes. But I'm not talking of the correct value of the density for a certain
material, but I'm talking about how to find a way to use density for
approximatig sss. Constant density doesn't give very good results for
certain material near the contour.

> You can use any function or pattern as the media density; working out
> the function itself is probably impossible if you are using meshes.

Yes, meshes are a limit. And functions or patterns works well for simple
objects, but not for complicated objects, CSGs, blobs, etc. And I say more:
isosurfaced can be used... The generating function can be used for
extracting the formula of the density for many and many surfaces...

But we always come to the same point... Why not to develop a simpler method
for approximating sss using media? Mine is only an idea and I dont know if
I'll be able to complete it or if it works at all. It has many limits at
the moment, because only a few persons have helped me in these groups. I've
obtained very good results at the moment and I hope to release the sources
one day. On the other side we could simulate sss or bssrdf, but it's not
the case... As Christoph said, we have the powerful of medias that can
approximate sss effects. But aren't media a bit complicated to model?

Certainly the code of Sarah Tariq should be better... But we haven't it! :-/

A.

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"Antonio Ferrari" <nomail@nomail> wrote:

> P.S. The source code of Sarah Tariq is not available. Can anyone try to
> contact her?

If you click on Home you end up at
http://www-static.cc.gatech.edu/grads/t/Sarah.Tariq/index.html. I believe
her email address is written just under Georgia Institute of Technology,
with an @ written in letters. ;-)

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